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2024年5月31日 · On this basis the cycle is described as starting with about five days of menstruation, followed by a proliferative phase that lasts to about the 14th day, and then a secretory phase that lasts until the next menstruation. The external manifestation of menstruation depends upon cyclical change in the lining of the body of the uterus.
The female reproductive system. The female gonads, or sexual glands, are the ovaries; they are the source of ova (eggs) and of the female sex hormones estrogens and progestogens. The fallopian, or uterine, tubes conduct ova to the uterus, which lies within the lesser or true pelvis. The uterus connects through the cervical canal with the vagina.
halogen, any of the six nonmetallic elements that constitute Group 17 (Group VIIa) of the periodic table.The halogen elements are fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). They were given the name halogen, from the Greek roots hal- (“salt”) and -gen (“to produce”), because they all produce sodium salts of similar properties, of which ...
human digestive system. Also called: digestive tract. Or: alimentary canal. Key People: Berkeley George Andrew Moynihan, 1st Baron Moynihan. Related Topics: stomach. esophagus. pharynx. mouth. intestine. gastrointestinal tract, pathway by which food enters the body and solid wastes are expelled.
3 天前 · pollination, transfer of pollen grains from the stamens (the flower parts that produce them) to the ovule-bearing organs or to the ovules (seed precursors) themselves. In gymnosperm plants such as conifers and cycads, in which the ovules are exposed, the pollen is simply caught in a drop of fluid secreted by the ovule.
2024年4月16日 · What is a chloroplast? Where are chloroplasts found? Why are chloroplasts green? Do chloroplasts have DNA? chloroplast, structure within the cells of plants and green algae that is the site of photosynthesis, the process by which light energy is converted to chemical energy, resulting in the production of oxygen and energy-rich organic compounds.
gallium. Key People: Paul-Émile Lecoq de Boisbaudran. Related Topics: chemical element. boron group element. gallium (Ga), chemical element, metal of main Group 13 (IIIa, or boron group) of the periodic table. It liquefies just above room temperature.
